Flow Magnetic

7/29/2019 Flow Magnetic

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Copyright Copperhill and Pointer, Inc., 2004 (All Rights Reserved)

The Consumer Guide to

Magnetic Flowmeters

Seminar Presented by

David W. Spitzer

Spitzer and Boyes, LLC

+1.845.623.1830

Spitzer and Boyes, LLC (+1.845.623.1830)


2

Copyright

This document may be viewed and printed for

personal use only.

No part of this document may be copied, reproduced,

transmitted, or disseminated in any electronic or non-

electronic format without written permission.

All rights are reserved.

Copperhill and Pointer, Inc.



3

Disclaimer

The information presented in this document is for the

general education of the reader. Because neither the

author nor the publisher have control over the use of

the information by the reader, both the author and publisher disclaim any and all liability of any kind

arising out of such use. The reader is expected to

exercise sound professional judgment in using any of

the information presented in a particular application.



Seminar Presenter





4

Disclaimer

The full and complete contents of this document are for

general information or use purposes only. The contents are provided “as is” without warranties of any kind, either expressed or implied, as to the quality, accuracy, timeliness,completeness, or fitness for a general, intended or particular

purpose. No warranty or guaranty is made as to the resultsthat may be obtained from the use of this document. Thecontents of this document are “works in progress” that will be revised from time to time.



Seminar Presenter



5

Disclaimer

Spitzer and Boyes, LLC and Copperhill and Pointer, Inc.have no liability whatsoever for consequences of any actionsresulting from or based upon information in and findings of this document. In no event, including negligence, will Spitzer and Boyes, LLC or Copperhill and Pointer, Inc. beliable for any damages whatsoever, including, without limitation, incidental, consequential, or indirect damages, or loss of business profits, arising in contract, tort or other theory from any use or inability to use this document.



Seminar Presenter



6

Disclaimer

The user of this document agrees to defend, indemnify,

and hold harmless Spitzer and Boyes, LLC and

Copperhill and Pointer, Inc., its employees,

contractors, officers, directors and agents against all liabilities, claims and expenses, including attorney’s

fees, that arise from the use of this document.



Seminar Presenter





7

Disclaimer

The content of this seminar was developed in animpartial manner from information provided by

suppliers

Discrepancies noted and brought to theattention of the editors will be corrected

We do not endorse, favor, or disfavor any particular supplier or their equipment



Seminar Presenter



8

Seminar Outline

Introduction

Fluid Flow Fundamentals

Flowmeter Technology

Flowmeter Performance

Consumer Guide



9

Introduction

Working Definition of a Process

Why Measure Flow?





10

Working Definition of a

Process

A process is anything that changes



11

Why Measure Flow?

Flow measurements provide information

about the process

The information that is needed depends

on the process



12

Why Measure Flow?

Custody transfer

Measurements are often required to

determine the total quantity of fluid that passed through the flowmeter for billing

purposes





13

Why Measure Flow?

Monitor the process Flow measurements can be used to ensure

that the process is operating satisfactorily



14

Why Measure Flow?

Improve the process

Flow measurements can be used for heat and

material balance calculations that can be

used to improve the process



15

Why Measure Flow?

Monitor a safety parameter

Flow measurements can be used to ensure

that critical portions of the process operate safely





16

Seminar Outline

Introduction Fluid Flow Fundamentals



Consumer Guide



17


Temperature

Pressure

Density and Fluid Expansion

Types of Flow

Inside Pipe Diameter

Viscosity

Reynolds Number and Velocity Profile

Hydraulic Phenomena



18

Temperature

Measure of relative hotness/coldness

Water freezes at 0°C (32°F)

Water boils at 100°C (212°F)





19

Temperature

Removing heat from fluid lowerstemperature

If all heat is removed, absolute zero

temperature is reached at

approximately -273°C (-460°F)



20

Temperature

Absolute temperature scales are

relative to absolute zero temperature

Absolute zero temperature = 0 K (0°R)

Kelvin = °C + 273

° Rankin = °F + 460



21

Temperature

Absolute temperature is important

for flow measurement





22

Temperature

0 K = -273°C 0°R = -460°F

460°R = 0°F273 K = 0°C

3 73 K = 100 °C 6 72 °R = 21 2°F



23

Temperature

Problem

The temperature of a process

increases from 20°C to 60°C. For

the purposes of flow measurement,

by what percentage has the

temperature increased?



24

Temperature

It is tempting to answer that the

temperature tripled (60/20), but the

ratio of the absolute temperatures is

important for flow measurement

(60+273)/(20+273) = 1.137

13.7% increase





25


Temperature

Pressure


Types of Flow


Viscosity


Hydraulic Phenomena



26

Pressure

Pressure is defined as the ratio of a

force divided by the area over which

it is exerted (P=F/A)



27

Pressure

Problem

What is the pressure exerted on a table by

a 2 inch cube weighing 5 pounds?

(5 lb) / (4 inch2 ) = 1.25 lb/in2

If the cube were balanced on a 0.1 inch

diameter rod, the pressure on the table

would be 636 lb/in2





28

Pressure

Atmospheric pressure is caused bythe force exerted by the atmosphere

on the surface of the earth

2.31 feet WC / psi

10.2 meters WC / bar



29

Pressure

Removing gas from a container

lowers the pressure in the container

If all gas is removed, absolute zero

pressure (full vacuum) is reached at

approximately -1.01325 bar (-14.696

psig)



30

Pressure

Absolute pressure scales are relative

to absolute zero pressure

Absolute zero pressure

Full vacuum = 0 bar abs (0 psia)

bar abs = bar + 1.01325

psia = psig + 14.696





31

Pressure

Atmosphere

Absolute Zero

Vacuum

Absol ut e Ga ug eDifferential



32

Pressure

Absolute pressure is important for

flow measurement



33

Pressure

Problem

The pressure of a process increases

from 1 bar to 3 bar. For the

purposes of flow measurement, by

what percentage has the pressure

increased?





34

Pressure

It is tempting to answer that the pressure tripled (3/1), but the ratio

of the absolute pressures is


(3+1.01325)/(1+1.01325) = 1.993

99.3% increase



35


Temperature

Pressure


Types of Flow


Viscosity


Hydraulic Phenomena



36


Density is defined as the ratio of the

mass of a fluid divided its volume

( ρ=m/V)





37


Specific Gravity of a liquid is theratio of its operating density to that

of water at standard conditions

SG = ρ liquid / ρ water at standard conditions



38


Problem

What is the density of air in a 3.2 ft3

filled cylinder that has a weight of

28.2 and 32.4 pounds before and

after filling respectively?



39


The weight of the air in the empty

cylinder is taken into account

Mass =(32.4-28.2)+(3.2•0.075)

= 4.44 lb

Volume = 3.2 ft 3

Density = 4.44/3.2 = 1.39 lb/ft 3





40


The density of most liquids is nearlyunaffected by pressure

Expansion of liquids

V = V 0 (1 + β • ΔT)

V = new volume

V 0 = old volume

β = cubical coefficient of expansion

ΔT = temperature change



41


Problem

What is the change in density of a

liquid caused by a 10°C temperature

rise where β is 0.0009 per °C ?



42


Calculate the new volume

V = V 0 (1 + 0.0009•10) = 1.009 V 0

The volume of the liquid increased to

1.009 times the old volume, so the new

density is (1/1.009) or 0.991 times the

old density





43


Expansion of solids V = V 0 (1 + β • ΔT)

where β = 3•α

α = linear coefficient of expansion

Temperature coefficient

Stainless steel temperature coefficient

is approximately 0.5% per 100°C



44


Problem

What is the increase in size of metal

caused by a 50°C temperature rise

where the metal has a temperature

coefficient of 0.5% per 100°C ?



45


Calculate the change in size

(0.5 • 50) = 0.25%

Metals (such as stainless steel) can

exhibit significant expansion





46


Temperature

Pressure


Types of Flow


Viscosity


Hydraulic Phenomena



47

Types of Flow

Q = A • v

Q is the volumetric flow rate

A is the cross-sectional area of the pipe

v is the average velocity of the fluid in the

pipe



48

Types of Flow

Typical Volumetric Flow Units(Q = A • v)

ft 2 • ft/sec = ft 3 /sec

m2 • m/sec = m3 /sec

gallons per minute (gpm)

liters per minute (lpm)

cubic centimeters per minute (ccm)





49

Types of Flow

W = ρ • Q W is the mass flow rate

ρ is the fluid density

Q is the volumetric flow rate



50

Types of Flow

Typical Mass Flow Units (W = ρ • Q)

lb/ft 3 • ft 3 /sec = lb/sec

kg/m3 • m3 /sec = kg/sec

standard cubic feet per minute (scfm)

standard liters per minute (slpm)

standard cubic centimeters per minute(sccm)



51

Types of Flow

Q = A • v

W = ρ • Q

Q volumetric flow rate

W mass flow rate

v fluid velocity

½ ρv2 inferential flow rate





52


Temperature

Pressure


Types of Flow


Viscosity


Hydraulic Phenomena



53


The inside pipe diameter (ID) is


Pipes of the same size have the same

outside diameter (OD)

Welding considerations

Pipe wall thickness, and hence its ID,

is determined by its schedule



54


Pipe wall thickness increases with

increasing pipe schedule

Schedule 40 pipes are considered

“standard” wall thickness

Schedule 5 pipes have thin walls

Schedule 160 pipes have thick walls





55


Nominal pipe size For pipe sizes 12-inch and smaller, the

nominal pipe size is the approximate ID of a

Schedule 40 pipe

For pipe sizes 14-inch and larger, the

nominal pipe size is the OD of the pipe



56


Temperature

Pressure


Types of Flow


Viscosity


Hydraulic Phenomena



57

Viscosity

Viscosity is the ability of the fluid to

flow over itself

Units

cP, cSt

Saybolt Universal (at 100ºF, 210 ºF)

Saybolt Furol (at 122ºF, 210 ºF)





58

Viscosity

Viscosity can be highly temperaturedependent

Water

Honey at 40°F, 80°F, and 120°F

Peanut butter



59


Temperature

Pressure


Types of Flow


Viscosity


Hydraulic Phenomena



60

Velocity Profile and

Reynolds Number

Reynolds number is the ratio of

inertial forces to viscous forces in

the flowing stream

R D = 3160 • Q gpm • SG / ( μcP • Din )





61


Reynolds Number

Reynolds number can be used as anindication of how the fluid is flowing in the pipe

Flow regimes based on R D

Laminar < 2000

Transitional 2000 - 4000

Turbulent > 4000



62


Reynolds Number

Not all molecules in the pipe flow at

the same velocity

Molecules near the pipe wall move

slower; molecules in the center of the

pipe move faster



63


Reynolds Number

Flow

Velocity Profile

Laminar Flow Regime

Molecules move straight down pipe





64


Reynolds Number

Flow

Velocity Profile

Turbulent Flow Regime Molecules migrate throughout pipe



65


Reynolds Number

Transitional Flow Regime

Molecules exhibit both laminar and turbulent

behavior



66


Reynolds Number

Many flowmeters require a good velocity

profile to operate accurately

Obstructions in the piping system candistort the velocity profile

Elbows, tees, fittings, valves





67


Reynolds Number

Flow

Velocity Profile (distorted)

A distorted velocity profile canintroduce significant errors into themeasurement of most flowmeters



68


Reynolds Number

Good velocity profiles can be developed

Straight run upstream and downstream

No fittings or valves

Upstream is usually longer and more important

Flow conditioner

Locate control valve downstream of

flowmeter



69


Temperature

Pressure


Types of Flow


Viscosity


Hydraulic Phenomena





70

Hydraulic Phenomena

Vapor pressure is defined as the pressure at which a liquid and its

vapor can exist in equilibrium

The vapor pressure of water at 100°C is

atmospheric pressure (1.01325 bar abs)

because water and steam can coexist



71

Hydraulic Phenomena

A saturated vapor is in equilibrium

with its liquid at its vapor pressure

Saturated steam at atmospheric

pressure is at a temperature of 100°C



72

Hydraulic Phenomena

A superheated vapor is a saturated

vapor that is at a higher temperature

than its saturation temperature Steam at atmospheric pressure that is at

150°C is a superheated vapor with 50°C

of superheat





73

Hydraulic Phenomena

Flashing is the formation of gas(bubbles) in a liquid after the

pressure of the liquid falls below its

vapor pressure

Reducing the pressure of water at

100°C below atmospheric pressure (say

0.7 bar abs) will cause the water to boil



74

Hydraulic Phenomena

Cavitation is the formation and

subsequent collapse of gas (bubbles)

in a liquid after the pressure of the

liquid falls below and then rises

above its vapor pressure

Can cause severe damage in pumps and

valves



75

Hydraulic Phenomena

Distance

Pressure

Flashing

Cavitation

Piping Obstruction

Vapor Pressure (typical)





76

Hydraulic Phenomena

Energy Considerations Claims are sometimes made that

flowmeters with a lower pressure drop

will save energy



77

Hydraulic Phenomena

Energy Considerations

Pressure

Flow

Centrifugal

Pump Curve



78

Hydraulic Phenomena


Pressure

Flow

System Curve

(without flowmeter)





79

Hydraulic Phenomena


Flow

Pressure



80

Hydraulic Phenomena


Flow

P

Q

System, Flowmeter

and Control Valve

Pressure

System

Flowmeter and

Control Valve

Pressure Drop

System and Flowmeter



81

Hydraulic Phenomena


Flow

P

Q

System, Flowmeter

and Control Valve

Pressure

System

Flowmeter and

Control Valve

Pressure Drop


(Low Pressure Drop)





82

Hydraulic Phenomena

Energy Considerations The pump operates at the same flow and

pressure, so no energy savings are

achieved by installing a flowmeter with

a lower pressure drop



83

Hydraulic Phenomena


Flow

P

Q

Pressure

System


Full Speed

Reduced Speed



84

Hydraulic Phenomena


Operating the pump at a reduced speed

generates the same flow but requires alower pump discharge pressure

Hydraulic energy generated by the pump

better matches the load

Energy savings are proportional to the

cube of the speed





85

Seminar Outline




Consumer Guide



86

Magnetic Flowmeter

Technology

Principle of Operation

Flowmeter Designs

Transmitter Designs

Installation

Accessories

Other Flowmeter Technologies



87


Faraday’s Law of Electromagnetic

Induction defines the magnitude of the

voltage induced in a conductive mediummoving at a right angle through a

magnetic field

Most notably applied to electrical power

generation





88


Faraday’s Law

E = constant • B • L • v

B is the magnetic flux density

L is the path length

v is the velocity of the medium



89


Experiment

Galvanometer with wire between terminals

Horseshoe magnet

Moving the wire through the magnetic field

moves the galvanometer indicator

Moving wire in opposite direction moves

indicator in opposite direction

Moving wire faster moves indicator higher



90


Flow

Electrode

Magnet

Tube (non-magnetic)Liner (insulating)

Magnetic Field





91


Magnetic flowmeters direct electromagnetic energy into the flowing

stream

Voltage induced at the electrodes by the

conductive flowing stream is used to

determine the velocity of fluid passing

through the flowmeter



92


Induced voltage

E = constant • B • D • v

Substituting Q = A • v and assuming that

A, B, and D are constant yields:

E = constant • Q



93


The induced voltage at the electrodes is

directly proportional to the flow rate

E α Q





94


AC Excitation

Magnet is excited by an AC waveform Voltage waveform at electrode is also an

AC waveform



95


AC Excitation

AC excitation was subject to:

Stray voltages in the process liquid

Electrochemical voltage potential between

the electrode and process fluid



96


AC Excitation

AC excitation was subject to:

Inductive coupling of the magnets within the

flowmeter Capacitive coupling between signal and

power circuits

Capacitive coupling between interconnection

wiring





97


AC Excitation

Zero adjustments were used tocompensate for these influences and the

effect of electrode coating

Percent of full scale accuracy



98


AC Excitation

Feeding power to the primary element,

then back to the transmitter reduces the

possibility of inducing voltage from the

power wiring

Electromagnet is the large power draw

Signal voltage could be induced from wiring

carrying current to the magnet



99


DC Excitation

Pulsed DC excitation reduces drift by

turning the magnet on and off

Magnet On = Signal + Noise

Magnet Off = Noise





100


DC Excitation

Noise is canceled by subtracting thesetwo measurements

Signal + Noise – Noise = Signal



101


DC Excitation

DC magnetic flowmeters automatically

self-zero

Percent of rate accuracy

The 4mA analog output zero adjustment is

not set automatically and still maintains a

percent of full scale accuracy



102


DC Excitation

Response time can be compromised





103

Magnetic Flowmeter

Technology

Principle of Operation Flowmeter Designs

Transmitter Designs

Installation

Accessories




104

Magnetic Flowmeter Designs

Ceramic

Electrodeless

Low Flow

Medium Flow

High Flow



105


High Noise

Low Conductivity

Partially-full

Response - Fast

Sanitary

Two-wire





106


External/Internal Coils Flanged

Wafer

Miniature



107

Magnetic Flowmeter

Technology


Flowmeter Designs

Transmitter Designs

Installation

Accessories




108

Magnetic Transmitter Designs

Analog

Electrical components subject to drift

AC and DC designs

Four-wire design





109


Digital Microprocessor is less susceptible to drift

Mathematical characterization in software

Remote communication (with HART)

Four-wire design

Mostly DC designs

Can usually retrofit AC magnetic flowmeters

using the existing primary element



110


Digital (Two-wire)

Microprocessor is less susceptible to drift

Mathematical characterization in software

Remote communication (with HART)

Two-wire design

Installation savings

Low flow performance degraded

Response time degraded



111


Digital (Battery Power)

Microprocessor is less susceptible to drift

Used for totalization Wake up occasionally

Slow response





112

Magnetic Flowmeter

Transmitter Designs

Fieldbus Microprocessor is less susceptible to drift

Mathematical characterizations in software

Multi-drop wiring

Remote communication

Issues with multiple protocols



113

Magnetic Flowmeter

Technology


Flowmeter Designs

Transmitter Designs

Installation

Accessories




114

Installation

Fluid Characteristics

Piping and Hydraulics

Grounding

Electrical

Ambient Conditions

Setup Information





115


Liquids only Water

Slurries

Electrical conductivity of liquid must be

above minimum conductivity



116


Within accurate flow range

Corrosion and erosion

Electrode coating

Cleaning technique

High impedance electronics



117


Immiscible liquids

Ferromagnetic liquids

Hot/cold liquids

Ceramic liner damage due to sudden

temperature change

Gas in liquid stream





118


Keep flowmeter full of liquid Hydraulic design

Vertical riser preferred

Avoid inverted U-tube

Be careful when flowing by gravity

Orient electrodes in horizontal plane



119


Maintain good velocity profile

Locate control valve downstream of

flowmeter

Provide adequate straight run

Locate most straight run upstream

Install flow conditioner

Use full face gaskets



120


Sizing

Smaller sizes generally result in better

accuracy Larger sizes lower velocity and can reduce

pressure drop and erosion





121


Use proper mating flange 0.5 inch wafers installed between 1 inch

flanges

Wetted parts compatible with liquid



122

Grounding

Primaries with internal grounding

electrodes need no additional grounding



123

Grounding

Non-conductive pipe

Install grounding rings upstream and

downstream of primary and electrically bond transmitter to both

Conductive pipe

Electrically bond flowmeter to upstream and

downstream flange (or grounding ring)





124

Electrical

Integral primary/transmitter reducewiring cost

Remote mounting can increase

conductivity limit



125

Electrical

Wiring

Low voltage power supply can eliminate

power conduit

Two-wire magnetic flowmeters eliminate

power wiring

Fieldbus reduces wiring



126

Ambient Conditions

Outdoor applications (-20 to 60°C)

Many designs are for indoor locations

Submerged primary element

Leakage

Hazardous locations

Many designs are general purpose





127

Setup Information

GIGO (garbage in – garbage out) Entering correct information correctly is

critical

Size

Calibration factors

Scaling



128

Setup Information

Failure to use correct information can

cause significant error and startup

problems



129

Magnetic Flowmeter

Technology


Flowmeter Designs

Transmitter Designs

Installation

Accessories






130

Accessories

Primary NEMA 4, 6P, and IP67, 68

Temporary submersion

Direct burial

Ultrasonic cleaner



131

Accessories

Transmitter

NEMA 4, 4X and IP65, 67

Analog outputs

Active/passive

Dual/split range

Pulse output

Totalization and alarms

HART, Foundation Fieldbus, Profibus



132

Accessories

Transmitter

Empty pipe detection

Intrinsically safe electrode wiring Gas inside pipe

Electrode cleaning

Ultrasonic

High voltage

High impedance input (millions of meg-ohms)





133

Magnetic Flowmeter

Technology

Principle of Operation Flowmeter Designs

Transmitter Designs

Installation

Accessories




134


Coriolis Mass Insertion

Differential Pressure

Magnetic

Positive Displacement

Target

Thermal

Turbine

Ultrasonic

Vortex Shedding



135

Coriolis Mass Flowmeter

Coriolis mass flowmeters measure the

force generated as the fluid moves

towards/away from its center of rotation





136

Coriolis Mass Flowmeter

Flow



137

Differential Pressure Flowmeter

A piping restriction is used to develop a

pressure drop that is measured and used

to infer fluid flow

Primary Flow Element

Transmitter (differential pressure)



138

Orifice Plate


Flow

Orifice Plate





139

Venturi


Flow

Throat



140

Flow Nozzle


Flow

Nozzle



141

V-Conetm


Flow

V-Conetm





142


Pressure drop is proportional to the square of the fluid flow rate

Δ p α Q2 or Q α sqrt( Δ p)

Double the flow… four times the differential



143


Low flow measurement can be difficult

For example, only ¼ of the differential

pressure is generated at 50 percent of the

full scale flow rate. At 10 percent flow, the

signal is only 1 percent of the differential

pressure at full scale.



144

Magnetic Flowmeter

Fluid flow through a magnetic field

generates a voltage at the electrodes that

is proportional to fluid velocity Primary Flow Element

Transmitter





145

Magnetic Flowmeter

FlowElectrode

Magnet Tube (non-magnetic)Liner (insulating)



146

Magnetic Flowmeter

Traditional AC excitation was susceptible

to noise and drift

A low voltage signal is generated that is

susceptible to noise and cross-talk at the

excitation frequency



147

Magnetic Flowmeter

Pulsed DC excitation reduces drift by

turning the magnet on and off

Noise (while the magnet is off) is subtracted from signal and noise (while the magnet is

on) to reduce the effects of noise and cross-

talk

Response time can be compromised





148

Positive Displacement

Flowmeter

Positive displacement flowmetersmeasure flow by repeatedly entrapping

fluid within the flowmeter

Moving parts with tight tolerances

Bearings

Many shapes



149

Target Flowmeter

Target flowmeters determine flow by

measuring the force exerted on a body

(target) suspended in the flow stream



150

Target Flowmeter

Flow

Target





151

Thermal Flowmeter

Thermal flowmeters use the thermal properties of the fluid to measure flow

Hot Wire Anemometer

Thermal Profile



152

Thermal Flowmeter

Hot Wire Anemometer

Hot wire anemometers determine flow by

measuring the amount of energy needed

to heat a probe whose heat loss changes

with flow rate



153

Thermal Flowmeter

Hot Wire Anemometer

Flow

Thermal

Sensor





154

Thermal Flowmeter

Thermal Profile

Thermal profile flowmeters determine flow by measuring the temperature

difference that results in a heated tube

when the fluid transfers heat from the

upstream portion to the downstream

portion of the flowmeter



155

Thermal Flowmeter

Thermal Profile

Flow

Heater

Temperature Sensors

Heater

Zero Flow



156

Turbine Flowmeter

Fluid flow causes a rotor to spin whereby

the rotor speed is proportional to fluid

velocity Primary Flow Element

Transmitter





157

Turbine Flowmeter

Flow

Rotor

Sensor/Transmitter



158

Turbine Flowmeter

The sensor detects the rotor blades

The frequency of the rotor blades passing

the sensor is proportional to fluid velocity



159

Ultrasonic - Doppler

Doppler ultrasonic flowmeters reflect

ultrasonic energy from particles, bubbles

and/or eddies flowing in the fluid





160


Flow

Transmitter Receiver

Bubbles or Solids

Reflection



161


Under no flow conditions, the frequencies

of the ultrasonic beam and its reflection

are the same

With flow in the pipe, the difference

between the frequency of the beam and its

reflection increases proportional to fluid

velocity



162

Ultrasonic - Transit Time

Transit time (time-of-flight) ultrasonic

flowmeters alternately transmit ultrasonic

energy into the fluid in the direction and against the direction of flow





163


Flow

Sensor

Sensor



164


The time difference between ultrasonic

energy moving upstream and downstream

in the fluid is used to determine fluid

velocity



165

Under no flow conditions, the time for the ultrasonic energy to travel upstream

and downstream are the same

Flow

Sensor

Sensor






166


With flow in the pipe, the time for theultrasonic energy to travel upstream will

be greater than the downstream time

Flow

Sensor

Sensor



167

Vortex Shedding Flowmeter

A bluff body in the flow stream creates

vortices whereby the number of vortices

is proportional to the fluid velocity


Transmitter



168


Flow Vortex

Sensor





169


The sensing system detects the vorticescreated

The frequency of the vortices passing the

sensing system is proportional to fluid

velocity



170

Insertion Flowmeter

Insertion flowmeter infer the flow in the entire

pipe by measuring flow at one or more strategic

locations in the pipe

Differential Pressure

Magnetic

Target

Thermal

Turbine

Vortex



171

Insertion Flowmeter

Flow

Sensor





172

Seminar Outline




Consumer Guide



173



Performance Statements

Reference Performance

Pulse Output vs. Analog Output

Actual Performance

Supplier Claims



174


Accuracy is the ability of the

flowmeter to produce a measurement

that corresponds to its characteristiccurve





FlowError 0

Accuracy



176


Repeatability is the ability of the

flowmeter to reproduce a

measurement each time a set of

conditions is repeated



FlowError 0

Repeatability





178


Linearity is the ability of therelationship between flow and

flowmeter output (often called the

characteristic curve or signature of

the flowmeter) to approximate a

linear relationship



FlowError 0

Linearity



180


Flowmeter suppliers often specify the

composite accuracy that represents

the combined effects of repeatability,linearity and accuracy





FlowError 0

Flow Range

Composite Accuracy (in Flow Range)



182






Actual Performance

Supplier Claims



183


Percent of rate

Percent of full scale

Percent of meter capacity (upper

range limit)

Percent of calibrated span





184


1% of rate performance at different flow rates with a 0-100 unit flow

range

100% flow Æ 0.01•100 1.00 unit

50% flow Æ 0.01•50 0.50 unit

25% flow Æ 0.01•25 0.25 unit

10% flow Æ 0.01•10 0.10 unit



185


Flow%Rate

Error0

10

-10

1% Rate Performance



186


1% of full scale performance at

different flow rates with a 0-100 unit

flow range 100% flow Æ 0.01•100 1 unit = 1% rate

50% flow Æ 0.01•100 1 unit = 2% rate

25% flow Æ 0.01•100 1 unit = 4% rate

10% flow Æ 0.01•100 1 unit = 10% rate





Flow%Rate

Error0

10

-10

1% Full Scale Performance



188


1% of meter capacity (or upper range

limit) performance at different flow rates

with a 0-100 unit flow range (URL=400)

100% flow Æ 0.01•400 4 units = 4% rate

50% flow Æ 0.01•400 4 units = 8% rate

25% flow Æ 0.01•400 4 units = 16% rate

10% flow Æ 0.01•400 4 units = 40% rate



Flow0

10

-10

1% Meter Capacity Performance





190


Performance expressed as a percent of calibrated span is similar to full

scale and meter capacity statements

where the absolute error is a

percentage of the calibrated span



191


1% of calibrated span performance at

different flow rates with a 0-100 unit flow

range (URL=400, calibrated span=200)

100% flow Æ 0.01•200 2 units = 2% rate

50% flow Æ 0.01•200 2 units = 4% rate

25% flow Æ 0.01•200 2 units = 8% rate

10% flow Æ 0.01•200 2 units = 20% rate



Flow0

10

-10

1% of Calibrated Span Performance

(assuming 50% URL)





193


A calibrated span statement becomesa full scale statement when the

instrument is calibrated to full scale

A calibrated span statement becomes

a meter capacity statement when the

instrument is calibrated at URL



194


Performance specified as a percent of

rate, percent of full scale, percent of

meter capacity, and percent of calibrated

span are different



Flow%Rate

Error0

10

-10

1% Rate

1% Meter Capacity1% Full Scale

1% Calibrated Span

(50%URL)





196


Different and multiple performance statements may apply

0.05% full scale typical transmitter

0.10% full scale low range transmitter

0.50% rate 50-100% full scale

0.25% full scale 10-50% full scale



197


0.25% rate 1-10 m/s

0.0025 m/s 0.1-1 m/s

Velocity (m/s) Error

10.0 0.0250 m/s 0.25% rate

1.0 0.0025 m/s 0.25% rate

0.5 0.0025 m/s 0.50% rate

0.1 0.0025 m/s 2.50% rate

under 0.1 undefined undefined



198


Performance statements apply over a

range of operation

Turndown is the ratio of the maximum flow that the flowmeter will measure

within the stated accuracy to the

minimum flow that can be measured

within the stated accuracy





199


Performance statements can bemanipulated because their meaning

may not be clearly understood

Technical assistance may be needed

to analyze the statements



200






Actual Performance

Supplier Claims



201


Reference performance is the quality

of measurement at a nominal set of

operating conditions, such as:

Water at 20°C in ambient conditions of

20°C and 50 percent relative humidity

Long straight run

Pulse output





202


In the context of the industrial world,reference performance reflects

performance under controlled

laboratory conditions



203


Hypothetical flowmeter

1% rate 1-10 m/s

0.01 m/s 0.1-1 m/s

Undefined under 0.1 m/s



204


Example - Omission

Hypothetical flowmeter

1% rate 10-100% of flow

2% rate 5-10% of flow

Percent of flow could be assumed to

be percent of user’s full scale





205


Example - Omission If full scale is not adjustable, the

percent is a percent of meter

capacity!

0-100 unit range with URL=400 units

1% rate 40-100 units

2% rate 20-40 units



206


Example - Omission

Similarly, a percent of full scale

statement could really be a percent

of meter capacity statement



207


Problem

If the full scale is not adjustable,

what is the performance of a flowmeter with the following accuracy specifications?

1% full scale 10-100% flow

2%full scale 5-10% flow





208


Solution Magnetic flowmeters can operate

upwards of 10 m/s

Assume meter capacity is 10 m/s

In typical applications, liquid velocity is below 3 m/s

Assume a user range of 0-2 m/s



209


Solution

The calculated accuracy is:

0.01*10 m/s 1-2 m/s

5% rate at 2 m/s

10% rate at 1 m/s

0.02*10 m/s 0.5-1 m/s

40% rate at 0.5 m/s

Undefined under 1 m/s



210


Rate statements at high velocity are

often discussed

Errors at lower velocity are often

only mentioned with prompting

Progressive disclosure





211


Flowmeter Performance Performance Statements



Actual Performance

Supplier Claims



212


Most suppliers specify pulse output

performance

Analog output performance is typically

the pulse output performance plus an

absolute error



213


Problem

What is the error associated with a

4-20mA analog output that has an

error of 0.010 mA?





214


Solution The conversion error is:

0.010/(20-4) = 0.06% of full scale

Many flowmeters have analog output

errors of 0.10% of full scale



215


Solution

Flow 0.06% Full Scale

100 units 0.06*100/100 = 0.06% rate

50 “ 0.06*100/50 = 0.12 “

25 “ 0.06*100/25 = 0.24 “

10 “ 0.06*100/10 = 0.60 “



216


Solution

Flow 0.10% Full Scale

100 units 0.10*100/100 = 0.10% rate

50 “ 0.10*100/50 = 0.20 “

25 “ 0.10*100/25 = 0.40 “

10 “ 0.10*100/10 = 1.00 “





217


Some suppliers cannot provide ananalog output accuracy

specification, so the performance of

the analog output may be undefined



218


In some flowmeter designs, the

analog output error can be larger

than the flowmeter accuracy

Often applies to flowmeters with

percent of rate accuracy

Rate error increases at low flow rates



219


Problem

What is the performance of a magnetic

flowmeter analog output at 25% of full scale flow when its reference accuracy(at that flow rate) is 0.25% rate plus0.1% full scale?

0.25 + 0.1•100/25 = 0.65% rate

0.65% is almost triple 0.25%





220


Flowmeters with percent of full scale, meter capacity, and calibrated

span often include the analog output

error in their pulse accuracy

statement



221


Example

An analog output error of 0.10% of

full scale is usually neglected for a

flowmeter that exhibits 1% of full

scale performance.



222






Actual Performance

Supplier Claims





223

Actual Performance

Operating Effects Ambient conditions

Humidity

Precipitation

Temperature

Direct sunlight



224

Actual Performance

Many flowmeters are rated to 10-

90% relative humidity (non-

condensing)

Outdoor locations are subject to 100%

relative humidity and precipitation in

various forms



225

Actual Performance

Operating Effects

Can be significant, even though the

numbers seem small

Not published by most suppliers

Information is not generally available to

fairly evaluate actual performance





226

Actual Performance

Example The error (at 25 percent of scale and

a 0°C ambient) associated with a

temperature effect of 0.01% full

scale per °C can be calculated as:

0.01*(20-0)/25, or 0.80% rate



227

Actual Performance

Velocity Profile

Distorted velocity profile can affect

performance

Provide adequate straight run

Locate most of the straight run upstream

of the flowmeter

Install a flow conditioner



228

Actual Performance

Fluid Properties

Reference accuracy is determined

using a known fluid at known

conditions





229

Actual Performance

Fluid Properties Variation from reference conditions

may require calibration correlations

that can affect flowmeter performance

Different fluid composition

Different fluid temperature



230





Analog Output vs. Pulse Output

Actual Performance

Supplier Claims



231

Supplier Claims

High Turndown

Example - Hypothetical flowmeter

0.25% rate accuracy

1000:1 turndown

Sounds fantastic!





232

Supplier Claims

High Turndown Further investigation reveals

0.25% rate accuracy 0.5-10 m/s

0.00125 m/s accuracy 0.01-0.5 m/s

Measures 0.01-10 m/s 1000:1 turndown



233

Supplier Claims

High Turndown

Performance expressed as a percent of

rate degrades below 0.5 m/s

0.25% rate 0.50 m/s

1.25% rate 0.10 m/s

2.50% rate 0.05 m/s

12.50% rate 0.01 m/s



234

Supplier Claims

Low Flow Operation

Reference accuracy statement is

claimed to be valid down to essentially

zero flow





235

Supplier Claims

Low Flow Operation Reference accuracy statement

0.25% rate accuracy 0.5-10 m/s

0.00125 m/s accuracy 0.01-0.5 m/s



236

Supplier Claims

Low Flow Operation

Flowmeter operates at low flows, but

performance expressed as a percent of

rate is degraded

1.25% rate 0.10 m/s

2.50% rate 0.05 m/s

12.50% rate 0.01 m/s



237

Supplier Claims

High Accuracy

High accuracy claims often refer to

high flow rates that may not be

practical

Often disguised by omission

“0.25% accuracy” (omits rate, full scale,

meter capacity, calibrated span)





238

Supplier Claims

No Piping Obstructions Magnetic flowmeters have no piping

obstructions



239

Seminar Outline

Introduction




Consumer Guide



240

Consumer Guide

User Equipment Selection Process

Learn about the technology

Find suitable vendors

Obtain specifications

Organize specifications

Evaluate specifications

Select equipment





241

Consumer Guide

User Equipment Selection Process Performing this process takes time and

therefore costs money



242

Consumer Guide


Haphazard implementation with

limited knowledge of alternatives does

not necessarily lead to a good

equipment selection



243

Consumer Guide

Guide Provides First Four Items

Learn about the technology

Find suitable vendors

Obtain specifications

Organize specifications

Evaluate specifications

Select equipment





244

Consumer Guide

Guide Provides First Four Items Information focused on

technology

Comprehensive lists of suppliers

and equipment



245

Consumer Guide

Guide Provides First Four Items

Significant specifications

Lists of equipment organized to

facilitate evaluation



246

Consumer Guide


By providing the first four items, the Consumer

Guides: make technical evaluation and equipment

selection easier, more comprehensive, and

more efficient





247

Consumer Guide

User Equipment Selection Process By providing the first four items, the Consumer

Guides:

allow selection from a larger number of

suppliers

simplifies the overall selection process



248

Consumer Guide

Supplier Data and Analysis

Attachments

Flowmeter categories

Availability of selected features

Models grouped by performance



249


Primary Limits

Size

1-3000+ mm

NEMA 4X, IP67 (IP68 available)





250


Primary Limits Ambient temperature

Typically limited by process

Process temperature

-20 to 130°C typical

Higher for ceramic liners



251


Primary Limits

Liner - materials

Rubber, PTFE

Others (ceramic, FEP, PFA, soft rubber, hard

rubber, EDPM, PVC, polypropylene,

polyurethane)



252


Primary Limits

Electrode - materials

Stainless steel

Others (Hastelloy C, platinum, Monel)

Electrode seal - materials

Liner material

Viton, Kalrez O-rings





253


Process Operating Limits Pressure

Most designs are rated under 50 bar

Special designs 1500-2000 bar



254


Process Operating Limits

Temperature

PTFE 130-150°C

PFA 180°C

Rubber/PP 70-90°C

Ceramic liners can be damaged by excessive

temperature change



255


Process Operating Limits

Conductivity

Over 1-5 μS/cm

Low conductivity designs to 0.01 μS/cm





256


Primary Installation/Maintenance Velocity profile

3-5D upstream typical

2-3D downstream typical

Some designs include straight run

Small diameters



257


Primary Installation/Maintenance

Electrode replacement

Field removable

Accuracy changes

Electrode maintenance

Coating

Corrosion



258


Primary Installation/Maintenance

Grounding ring maintenance

Check electrical connections

Corrosion

Grounding electrode

Electrode cleaning





259


Transmitter 4-wire device (separate power/analog wires)

Using DC power can eliminate power conduit

Typically measure forward and reverse flow



260


Transmitter

Outputs (active/passive)

Pulse

Analog (4-20 mA) (isolated)

Flow alarms

Empty pipe detection

Fault



261


Transmitter

Totalization

Forward, reverse, net, batch





262


Transmitter Mounting

Integral

Remote

50-200 m

Distance can increase conductivity limit (preamp)



263


Transmitter

Hazardous locations

Many are general purpose

NEC500 - Division 2 (non-incendive)

NEC500 - Division 1

Zone 1 and Zone 2

Intrinsically safe

Electrodes

Two-wire transmitters



264


Transmitter

Some models to not allow adjustment of full

scale Range adjustment mechanism provide

insight into age of design

Analog (potentiometer)

Dip switch

Digital





265


Performance Typically based on pulse output over a range

of velocity

Performance degrades at low velocity

In some designs, reference accuracy is

different for different ranges



266


Performance

Analog output accuracy

Adds 0.03-0.10% full scale (or more) to

reference accuracy

Analog output is inferior to pulse output

Some suppliers could not quantify

Some suppliers include the analog output

accuracy in the reference accuracy



267


Performance

It can be difficult to compare the

performance of different suppliers’ equipment





268


Operating Effects Ambient

Temperature, humidity

Process conditions

Temperature, pressure, pipe material,

composition

Power supply voltage



269


Operating Effects

It can be difficult to compare the operating

effects of different suppliers’ equipment



270

Consumer Guide


Attachments

Flowmeter categories

Availability of selected features

Models grouped by performance





271

Flowmeter Categories

Summary of offerings Categories

Manufacturing location/source



272

Flowmeter Categories

Suppliers (70)

Manufacturers (53)

11 USA

8 Czech Republic

8 China

7 Germany

7 Japan

5 Italy



273

Availability of Selected

Features

Hazardous location approvals

Submersible

High pressure (over 100 bar)

High input impedance (over 106 M Ω )

Batching





274

Availability of Selected

Features

Communications HART

Foundation Fieldbus

Profibus



275

Models Grouped by

Performance

Types of magnetic flowmeters

Outputs

Pulse/analog



276

Models Grouped by

Performance

Operating conditions

0-2 m/s calibration

For each category and for each output (pulse/analog), magnetic flowmeters are

grouped by their performance at 0.1 m/s





277

Review and Questions




Consumer Guide


The Consumer Guide to

Magnetic Flowmeters

Seminar Presented by

David W. Spitzer


Flow Magnetic

Documents

Transcript of Flow Magnetic